#1. Go Hiking in the Woods - Take your camera, the family dog, friends and family with you. There are plenty of locations in or near Toronto you can visit. eg. Try visiting Hilton Falls near Milton Ontario, just west of Toronto. The conservation area has both hiking and cycling paths, and a waterfalls you can walk behind.
#2. Go Cycling in the Woods / Pretty Neighbourhoods in Toronto. Two of my favourite locations to cycle through is Rosedale and the University of Toronto campus. (And yes, you can still take the dog with you.)
#3. Go Swimming at the Beach - September and early October is still warm enough to go swimming. Or try out one of Toronto's many indoor pools.
#4. Go Canoeing / Kayaking - You can rent canoes and kayaks in several locations in Toronto. Also makes a fun activity for a date or a family outing. If you own your own kayak or canoe, even better - but if you don't then you can also rent them.
#5. Baseball / Softball - The cooler temperatures make for great baseball weather. So even if you're just playing catch with a friend or practicing your swing at the local ball diamond, baseball is a good ol' fashioned fun activity. Don't like baseball? Try road hockey, football, archery, golf, tennis, basketball and a dozen other sports you can do outside.
I even found an "archery baseball" portable target people can use for playing an amusing game.
#6. Ultimate Zombie Tag / Capture the Flag - the game of children has been transformed into a sport for adults. Think larger scale games of hundreds of adults playing tag or capture the flag or similar games. The rules are simple, and it makes for an amazing good time for friends who want to join in for such large social / sporting activity.
In 2011 the website newmindspace.com organized a large urban Capture the Flag event in downtown Toronto in the financial district / Toronto City Hall. Recently in NYC they also organized a "Lightsaber Battle", as well as "Pillow Fight Days", Bubble Battles and other silly events.
Note - You don't have to wait for NewMindSpace to organize an event. You could just organize your own or find a different group that organizes similar events.
#7. Rake Leaves + Leaf Fight / Leaf Wrestling.
Step One - Pile all the leaves together.
Step Two - Fight like tigers playing together!
(The above photo was too cute NOT to add here.)
#8. Cleaning out the Garage - Just kidding. That isn't much fun. But it is much more fun what you can do with your garage during the Autumn (and Winter) once you've thrown out some junk you don't need. It gives you more space to put a hockey net or two, to store your kayak, baseball bat/gloves/balls, bicycles, walking sticks,